Finger print powder



Patented Nov. 16, 1937 UNITED STATES PATENT OFFICE FINGER PRINT POWDER Justin J. McCarthy, Boston, Mass.

6 Claims.

This application is a. division of one filed by me on March 14th, 1935, Serial No. 11,105 now Patent No. 2,028,619 issued Jan. 21, 1936.

This invention relates to a finger print powder.

At the present time when conditions such as poor light, inaccessibility, et cetera, make it difiicult or impossible to obtain a photograph of finger prints, it is the custom to sprinkle powder on said finger prints, and after brushing off the 10 surplus powder, taking an impression by means of a piece of tape. The impression so obtained is not as clear and distinct as it should be, and it is my object to produce an entirely new powder, which when used in combination with a sensi- 15 tized sheet treated with a solution, will obtain finger print impressions which are distinct and clear. My method of obtaining finger prints is fully described in said application filed March 14th, 1935, Serial No. 11,105.

20 My new finger print powder preferably consists of hydroquinone and acacia ground together. Best results are obtained if the powder is ground fine enough to pass through silk. The hydroquinone should preferably exceed the aca- 25 cia by weight; and I have secured good results by using eight parts hydroquinone and one part acacia by weight, although this proportion can be varied considerably and still obtain satisfactory results. The hydroquinone is a reducing agent in an alkaline solution, and other reducing agents such as metol could be used, although I prefer hydroquinone. Likewise the acacia is a water soluble gum, and while I prefer acacia, other water soluble gums might be used. Acacia is sometimes called gum arabic. It acts as a binder between the finger print and the powder 5 of which it forms a part.

What I claim is:

1. A finger print powder comprising hydroquinone and acacia, the said hydroquinone exceeding the said acacia in said powder by weight. 10

2. A finger print powder comprising hydroquinone and acacia, the said hydroquinone exceeding the said acacia in said powder more than double by weight.

3. A finger print powder comprising hydroqui- 15 none, and a water soluble gum, said hydroquinone exceeding said gum more than double by weight.

4. A finger print powder comprising hydroquinone, and a water soluble gum, the said hydroquinone exceeding the said water soluble gum in 2 said powder by weight.

5. A finger print powder comprising a plurality of parts by weight of hydroquinone, and one part by weight of acacia, the two being ground together into a powder fine enough to pass through 25 silk.

6. A finger print powder comprising eight parts by weight of hydroquinone and one part by weight of acacia.

JUSTIN J. MCCARTHY. 3o 

